[ 1.21.1 ] I cant get my structure to be generated

The game finds the structure but it wont generate
structure_set:
{
  "type": "minecraft:jigsaw",
  "biomes": [
    "minecraft:flower_forest",
    "minecraft:forest",
    "minecraft:plains"
  ],
  "step": "surface_structures",
  "terrain_adaptation": "none",
  "spawn_overrides": {},
  "start_pool": "project_zero_limit:oni_arena",
  "size": 1,
  "start_height": {
    "absolute": 0
  },
  "project_start_to_heightmap": "WORLD_SURFACE_WG",
  "max_distance_from_center": 1,
  "use_expansion_hack": false
}

structure:
{
  "structures": [
    {
      "structure": "project_zero_limit:oni_arena",
      "weight": 4
    }
  ],
  "placement": {
    "type": "minecraft:random_spread",
    "spacing": 25,
    "separation": 5,
    "salt": 0
  }
}

template_pool:
{
  "name": "project_zero_limit:oni_arena",
  "fallback": "minecraft:empty",
  "elements": [
    {
      "weight": 4,
      "element": {
        "element_type": "minecraft:single_pool_element",
        "projection": "rigid",
        "location": "project_zero_limit:oni_arena",
        "processors": "minecraft:empty",
        "override_liquid_settings": "ignore_waterlogging"
      }
    }
  ]
}